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Ultrasound blasts away tumour cells

By Andy Coghlan

An experimental technique that destroys cancer cells without drugs, surgery or radiation is showing promise in the lab. British company Gendel says that it has used blasts of ultrasound to destroy tumour cells in mice.

Can a two-pronged effect shrink tumours?

Gendel has been quietly refining its procedure for two years – and hopes that if human trials are successful when they start in two years’ time, its technology may lead to a non-invasive cancer therapy for tackling tumours that are hard to treat conventionally, such as those of the head and neck.

The technique relies on the application of an electric field to a tumour to make it susceptible to a follow-up blast of ultrasound. The combination appears to cause tumour cells to self-destruct.

The combined electric field and ultrasound (CEFUS) technology is based on a similar procedure Gendel – based in Coleraine, Northern Ireland – is developing to deliver drugs to difficult-to-reach parts of the body using a patient’s own red blood cells as a drug shuttle.

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Once “sensitised” outside the body with an electric field, the membranes of the red blood cells become permeable, in a process known as electroporation, and can be filled with a drug before they are returned to the patient. When ultrasound is beamed at the site where the drug is needed, the sensitised cells burst open, spilling the drug in the right place.

Porous cells

As the blood-based idea progressed to the stage where it will be tested later in 2003 in people for the first time, Gendel founders Tony McHale and Les Russell wondered if it would be possible to destroy tumour cells with the same combination of electric field and ultrasound.

It worked both on tumour cells in vitro, and more recently on tumours in at least 50 mice. A slight tumour regrowth was eliminated by boosting electric field and ultrasound levels.

But the Gendel team still does not know why the porous cells rupture when exposed to ultrasound. Neither treatment works on its own (see graph). Maybe the electric field makes the tumour cells permeable, so the cell is that little bit weaker when exposed to ultrasound, says McHale. Whatever the mechanism, Gendel believes the combined effect is to induce the cells to self-destruct.

If the technology ever becomes viable, Gendel hopes to treat both accessible tumours, such as those on the skin, as well as those on the gullet and mouth. For external applications, the electric field could be applied using conductive adhesive pads. For internal use, needle electrodes would be used.

“The tissue simply disappears and gets absorbed back into the body,” says Russell. The aim is to produce a portable device with disposable electrodes that contains kit for both internal and external procedures. Aside from time for anaesthesia, the whole procedure would probably take little more than five minutes.

Collateral damage

The electrosensitisation process might need to be applied under local anaesthetic. But the ultrasound fields applied – though stronger than those used to image babies in the womb – are of a strength routinely applied to muscles in sports medicine.

Gendel’s equipment would be tuned to deliver an appropriate dose of ultrasound to the tumour mass, but some healthy cells would inevitably be hit too. However, Russell points out that conventional surgery and radiation therapy have the same collateral damage problem.

But many cancer treatments have shown promise in animals only to fail in humans. Reinforcing the need for scepticism at this very early stage, a spokesman for Cancer-Research UK says Gendel’s work should be treated with “absolute caution” until more information is available.